This comprehensive guide to X and Y chromosome aneuploidy is written in lay language for affected individuals and their families, providing an authoritative volume that explains X and Y chromosome variations in clear and accurate terms. These surprisingly common genetic conditions, affecting 1 in 500 individuals, include Klinefelter syndrome, Trisomy X and 47,XYY. This guide provides a lifespan approach to the three trisomy conditions, as well as their less common variations involving 48 and 49 chromosomes. Readers are provided clear explanations of the genetics involved, diagnosis and disclosure issues, development from infancy through early adulthood, potential health and fertility concerns, and educational and psychosocial considerations. The text is illustrated with actual quotations from those who live with the disorders, and provides not only descriptions of potential concerns, but also strategies for successfully addressing the challenges that may develop.